Pressure-modulated hydraulic control valve

ABSTRACT

A pressure-modulated hydraulic control valve is provided for controlling fluid flow to engage and disengage a differential lock. A manual actuator acts through a modulating spring to shift a spool valve to selectively establish conditions in the control valve for engaging and disengaging the differential lock and the manual actuator includes a length adjustable link which may be adjusted without disassembly to change the modulating force to desired values. A check valve in the pressure port normally prevents flow to the spool valve when the lock is disengaged and a pin extends from the check valve into the valve bore and is engaged and moved by a ramp on the spool valve to unseat the check valve when the spool valve is shifted to establish the condition for engaging the lock.

United States Patent Schletzbaum et al.

[54] PRESSURE-MODULATED HYDRAULIC CONTROL VALVE [72] Inventors: John Wayne Schletzbaum, Hudson; Reno Antonio Rodeghiero, Cedar Falls, both of Iowa [73] Assigneei Deere 8: Company, Moline, Ill.

[22] Filed: Oct. 22, 1969 {21] Appl. No.: 868,498

s21 u.s.c1 ..137/ll6.3,137/625.69,303/50, 303/56 511 '1m.c1. ..B60t 15 04 531 FieldofSearch ..137/116.3,624.27,625.69; 303 50, 54, 56

[56] References Cited- UNITED STATES PATENTS 1,999,964 4/1935 Gustafson ..3o3/50 2,424,331 7 1947 Rose ..303 54 2,476,054 7/1949 Loweke. .....303/54 2,698,205 12/1954 Gagen ..303/54 1 1 June 6, 1972 2,844,166 7/1958 Edman ..l37/624.27 2,968,316 1/1961 Schultz ..137/625.69 X 3,473,566 10/1969 Peppel ..l37/625.69 X

Primary Examiner-Duane A. Reger Attorney-H. Vincent Harsha, Harold M. Knoth, William A. Murray, John M. Nolan and Jimmie R. Oaks [57] ABSTRACT.

A pressure-modulated hydraulic control valve is provided for controlling fluid flow to engage and disengage a differential lock. A manual actuator acts through a modulating spring to shift a spool valve to selectively establish conditions in the control valve for engaging and disengaging the differential lock and the manual actuator includes a length adjustable link which may be adjusted without disassembly to change the modulating force to desired values. A check valve in the pressure port normally prevents flow to the spool valve when the lock is disengaged and a pin extends from the check valve into the valve bore and is engaged and moved by a ramp on the spool valve to unseat the check valve when the spool valve is shifted to establish the condition for engaging the lock.

3 Claims, 2 Drawing Figures PRESSURE-MODULATED HYDRAULIC CONTROL VALVE I BACKGROUND OF THE INVENTION This invention relates to a pressure-modulating hydraulic control valve and more particularly relates to a control valve for a hydraulic differential lock.

Hydraulic differential locks are known in the art and the control valve of the present invention is particularly suited for use with a differential lock of the type disclosed in the commonly assigned U.S. Pat. No. 3,292,720 granted-to Harvey, Dec. 20; 1966.

The control valve presently used with the Harvey differential lock requires that the valve be disassembled for adjusting the modulating pressure and includes a poppet valve element, which is affected by changes-in the inlet pressure.

SUMMARY OF THE INVENTION According to the present invention, there is provided a pressure-modulating control valve, which has means for adjusting the modulating pressure without disassembling the valve.

Another object is to provide a control valve, which includes a spool valve element that remains unaffected by changes in inlet pressure.

A further object is to provide a check valve in the inlet, for blocking flow to the spool valve to substantially eliminate parasitic losses when the spool valve is in the position corresponding to disengagement of the differential lock, and a mechanical actuator for lifting the check valve from its seat when the spool valve element is shifted to the position corresponding to engagement of the differential lock.

Still a further object is to provide a control valve of simple and inexpensive construction.

These and other objects willbecome apparent from the ensuing detailed description and accompanying drawings.

BRIEF DESCRIPTION or THE DRAWINGS FIG. -1 is a fragmentary view, partly in elevation, partly schematic, and partly in section as respects the tractor differential and control valve, the parts illustrated in a condition in which the differential is locked.

FIG. 2 is a partialschematic and sectional view of the prior art control valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is shown a fragmentary section of a tractor differential of the type with which the control valve of the present invention is particularly adapted for use. The differential has an input shaft 12 which lies along the fore-and-aft axis A A of the tractor and carries a bevel pinion 14 that is meshed with a ring gear 16 of the differential 10. The ring gear is connected, in a conventional manner, to a differential carrier 17 which includes a plurality of differential pinions 18 in constant mesh with right and left-hand side gears 20 and 22 which are keyed respectively to rightand left-hand axles 24 and 26 having an axis B B perpendicular to the axis A A.

A multiple disk clutch28 is selectively engageable and disengageable between the left-hand side gear 22 and the carrier 17 by actuating a clutch piston 29. When the clutch is disengaged or released, the differential performs its normal function. When the clutch is engaged, the differential is locked up and the axles 24 and 26 are driven as one. It will be understood that the differential section illustrated in FIG. 1 is only the portion of the differential to the right-hand side of axis B B and that the clutch, clutch piston, ring gear, etc., are annular about the axis B B. The clutch piston 29 is hydraulically controlled by fluid pressure from a pump 30 through a differential control valve 32, having a pressure line 34 leading to the clutch via drilled passages that will be obvious without further description.

The differential control valve 32 includes a generally upright valve body 38 having a valve bore 40 formed therethrough. The lower end of the valve bore serves as a control port 42 and is connected to the pressure line 34 by means of a fitting44. Return and pressure ports 46 and 48 respectively intersect the bore at axially spaced locations intermediate the ends of the bore. The return port is connected to a fluid reservoir 49, and the pressure port is connected to the pump 30.

Arranged serially in the valve bore 40 from the bottom 'to the top thereof (FIG. 1) are a return spring 50, a valve spool 52, a pressure-modulating spring 54 and a valve plunger 56. The valve spool 52 includes an upper land 58 and a lower land 60 respectively separated from an intermediate land 62 by a pair of annular grooves. Extending in the valve. spool 52 between and fluidly interconnecting the bottom of the valve spool 52 with the annular groove located between the upper land 58 and the intermediate land 62 is a passage 64'. The valve spool 52 isshifted axially in the bore 40 among an upper position wherein the control port 44 is fluid-connected to the return port 46 to establish a released condition in the clutch 28, a lower position (that shown) wherein the control port 44 is fluid-connected to the pressure port 48 to establish an engaged condition in the clutch 28 and an intermediate position wherein the control and pressure ports 44 and 48 are blocked from each other and the return port to establish a hold condition in the clutch 28 wherein the latter is held engaged at a selected pressure. The position of the valve spool 52 and hence the condition of operation of the clutch 28 is dictated by the plunger 56, which is selectively shiftable axially in the bore between extreme upperand lower positions in the bore 40 in a manner to be described below. Specifically, when the plunger 56 is in the extreme upper position, the valve spool 52 is held in its upper position by the action of the return spring 50. As the plunger 56 moves downwardly, the action of the modulating spring 54 quickly overcomes the return spring 50 must be overcome in order to move the valve spool 52 from its lower to its intermediate position, increases as the modulating spring 54 ascends in the bore 40 and that the condition for establishing a maximum clutch'engaging pressure is effected by moving the plunger 56 to its lowermost position in the bore 40.

lands of the valve spool 52 when it occupies its upper position wherein the clutch 28 is disengaged, a check valve 68 is provided in the pressure port 48 and includes a check ball 70 biased against a seat 72 by a spring 74 to prevent flow into the valve bore 40. To open the check valve 68 to permit flow into the bore 40 when the valve spool 52 is shifted to its lower position for engaging the clutch, a pin 76 extends from the check ball 70 slightly into the bore 40 where it is engaged and shifted by an annular ramp 78 at the lower side of the intermediate land 62 to unseat the ball as the spool 52 is shifted downwardly.

A prior art control valve 1 10 is illustrated in FIG. 2 in order that applicants contribution to the art may be readily perceived. The control valve is generally similar to the control valve 32, described above, and includes a valve bore 112 in which a valve plunger 1 13 is manually shifted to act through a modulating spring 1 l4 and shift a flow control valve element 1 16. The modulating force of the spring 114 may be adjusted by disassembling the valve and adding or removing in trial and error fashion shims, such as 118, between the spring and the flow control valve element 1 16.

A poppet-type check valve is normally biased against a seat 122 by a spring 124 to prevent pressurized fluid from the In order to prevent parasitic losses or leakage across the pump 30 from flowing through a fluid passage 126 to the schematically shown differential clutch 28. When it is desired to engage the clutch 28, the valve plunger 112 is shifted toward the check valve to the position illustrated and the check valve is unseated by a pin 128 which is between the flow control valve element and the check valve. It is important to note that the check valve opens against the inlet pressure and its action is thus affected by changes in the line pressure, and therefore, the check valve is somewhat unstable in operation. Movement of the plunger to the left from the illustrated position disengages the clutch by connecting the clutch to the fluid resevoir via the bore. A manual control 130 is provided for shifting the valve plunger 112'and includes a bell crank 132 connected by means of an overcenter shiftable link 134 to the valve plunger.

The operation of the control valve 32 is briefly reiterated as follows:

A manual control linkage 80 is provided for selectively shifting the valve plunger 56 axially in the bore 40 between the aforementioned extreme upper and lower positions. The control 80 includes an on-off" pedal 82 pivotally mounted on a transverse horizontal pin 84 carried in a bracket 86, which is integral with and extends above the valve body 38. The pedal 82 is in the form of a bell crank having an upper arm or pad portion 88 and a lower arm 90, the latter being pivotally connected by means of a pin 92 to the upper end of a link 94. The lower end of the link 94 is pivotally connected to the top of the plunger 56 via a pin 96. The pivot pin 92 moves overcenter relative to the pivot pins 84 and 96 when the pedal 82 is pivoted between an on position, as shown, wherein it is prevented from further clockwise pivoting by a stop surface 98 on the bracket 86, and an off position wherein it is prevented from further counterclockwise pivoting by a stop pin 99 projecting from the bracket 86 into the path of movement of the pedal 82. The return spring 50 acts through the spool 52 and modulating spring 54 to maintain a constant upward bias on the plunger 56 and thus biases the pedal 82 against the surface 98 when the pin 92 is left of center as shown and biases the pedal 82 against the pin 99 when the pin 92 is to the right of center. The arrangement of the pedal 82 and link 94 is such that the valve plunger 56, and hence the modulating spring 54 are progressively shifted farther downwardly in the bore 40 as the pedal 82 is rotated from its "off" to its on position. As can be seen in FIG. 1, the pin 92 is only slightly to the left of center when the pedal 82 is in the on" position. Thus, the overcenter characteristic of the linkage defined by the pedal 82, link 94 and plunger 56 acts in conjunction with the stop surface 98 to effectively releasably hold the plunger 56 in its lowermost position once the pin 92 is moved to the left of center. It can then be appreciated that the maximum modulated pressure for engaging the clutch 28 can be obtained and maintained by moving the pedal 82 to and keeping the pedal 82 in its on" position.

For the purpose of increasing or decreasing the maximum pressure which can be developed for applying the clutch 28, the link 94 is constructed so as to be length-adjustable. Specifically, the link 94 includes an upper portion 100 and a lower portion 102, the lower portion including a stem 104 threaded into the upper portion. Adjustment is made by moving the link 94 into axial alignment with the bore 40 and then by turning the valve plunger 56 one way or the other for lengthening or shortening the link 94 as desired, respectively resulting in the plunger 56 being disposed a greater or lesser distance downwardly in the bore 40, which, of course, in turn results in the modulating spring 54 being respectively disposed at greater or lesser distance downwardly in the bore 40. Thus, adjustment of the maximum distance that the modulating spring 54 can be moved downwardly in the bore 40 correspondingly adjusts the maximum modulating force of the spring 54 and hence adjusts the maximum operating pressure which can be developed in the control port 44 and this adjustment may be accomplished without disassembling any part of the control valve 32.

We claim: l. A pressure-modulated control valve, comprising: a valve body defining a valve bore having pressure, return and control ports opening thereinto; a valve plunger, a compressible modulating spring, a valve member and a compressible return spring being serially arranged in said bore respectively from one end thereof, the valve plunger projecting from said one end; a manual control linkage means connected to said valve plunger and being movable between ofF and on" positions for respectively moving said plunger between first and second positions respectively of minimum and maximum extent into the bore; said return spring holding said valve member in a first position establishing fluid communication between said control and return ports when said control linkage means is in said off" position; the control port being so located relative to the valve member that pressure at the control port acts against the valve member and causes the latter to shift in the direction of the modulating spring; the valve plunger and modulating spring acting to shift the valve member from its first position to a second position establishing fluid communication between said control and pressure ports when the control linkage means is moved from said ofi to said on position and the fluid pressure at the control port then acting against the valve member to shift the latter to a third position, between the first and second positions, to block fluid communication among the control, pressure and return ports when the pressure at the control port is sufficient to overcome the modulating spring force resisting the movement of the valve member to the third position; said control linkage means including a length-adjustable link having one end pivotally connected to the valve plunger and being located relative to the latter such that lengthening and shortening the link will respectively increase and decrease the maximum extent that the valve plunger can be moved into the bore by the control linkage thus respectively increasing and decreasing the maximum modulating spring force to be overcome by the control pressure to move the valve member from its second to its third position when the control linkage means is in its on" position.

2. The invention defined in claim 1 wherein the length-adjustable link includes two portions, one being threadedly received in the other.

3. The invention defined in claim 2 wherein the control linkage includes pivotable means pivotally connected to the end of the link opposite from the end connected to the valve plunger and movable to dispose the link in axial alignment with said bore; whereby the length of the link may be adjusted by rotating the valve plunger. 

1. A pressure-modulated control valve, comprising: a valve body defining a valve bore having pressure, return and control ports opening thereinto; a valve plunger, a compressible modulating spring, a valve member and a compressible return spring being serially arranged in said bore respectively from one end thereof, the valve plunger projecting from said one end; a manual control linkage means connected to said valve plunger and being movable between ''''off'''' and ''''on'''' positions for respectively moving said plunger between first and second positions respectively of minimum and maximum extent into the bore; said return spring holding said valve member in a first position establishing fluid communication between said control and return ports when said control linkage means is in said ''''off'''' position; the control port being so located relative to the valve member that pressure at the control port acts against the valve member and causes the latter to shift in the direction of the modulating spring; the valve plunger and modulating spring acting to shift the valve member from its first position to a second position establishing fluid communication between said control and pressure ports when the control linkage means is moved from said ''''off'''' to said ''''on'''' position and the fluid pressure at the control port then acting against the valve member to shift the latter to a third position, between the first and second positions, to block fluid communication among the control, pressure and return ports when the pressure at the control port is sufficient to overcome the modulating spring force resisting the movement of the valve member to the third position; said control linkage means including a length-adjustable link having one end pivotally connected to the valve plunger and being located relative to the latter such that lengthening and shortening the link will respectively increase and decrease the maximum extent that the valve plunger can be moved into the bore by the control linkage thus respectively increasing and decreasing the maximum modulating spring force to be overcome by the control pressure to move the valve member From its second to its third position when the control linkage means is in its ''''on'''' position.
 2. The invention defined in claim 1 wherein the length-adjustable link includes two portions, one being threadedly received in the other.
 3. The invention defined in claim 2 wherein the control linkage includes pivotable means pivotally connected to the end of the link opposite from the end connected to the valve plunger and movable to dispose the link in axial alignment with said bore; whereby the length of the link may be adjusted by rotating the valve plunger. 